The invention relates to inflatable fabrics which comprise two separated and distinct fabric layers in discrete areas of such fabrics as well as connecting seam-producing materials (such as C-, Y-, X-, H-, U-, Z-, and W-shaped fabric materials, as merely examples) to which such fabric layers are attached. The resultant inflatable fabric composite this includes inflatable areas separated, at least partially, by seamed barrier areas. This configuration will form xe2x80x9cpillowedxe2x80x9d structures within the target fabric upon inflation. Such connecting seam-producing materials are incorporated within the two-layer structure as peel seams in relation with the individual fabric layers. Upon inflation, the seams then act as shear seams which greatly increases the overall strength of the two-layer inflatable fabric. These shear seams thus provide a relatively effective manner of reducing air permeability within the entire fabric article. Such a fabric may be utilized in numerous and various applications wherein fabric inflation is desired or necessary. In particular, the inventive fabric may be incorporated within an airbag cushion.
All U.S. patents cited herein are hereby fully incorporated by reference. Inflatable protective cushions used in passenger vehicles are a component of relatively complex passive restraint systems. The main elements of these systems are: an impact sensing system, an ignition system, a propellant material, an attachment device, a system enclosure, and an inflatable protective cushion. Upon sensing an impact, the propellant is ignited causing an explosive release of gases filing the cushion to a deployed state which can absorb the impact of the forward movement of a body and dissipate its energy by means of rapid venting of the gas. The entire sequence of events occurs within about 30 milliseconds. In the undeployed state, the cushion is stored in or near the steering column, the dashboard, in a door, or in the back of a front seat placing the cushion in close proximity to the person or object it is to protect.
Inflatable cushion systems commonly referred to as air bag systems have been used in the past to protect both the operator of the vehicle and passengers. Systems for the protection of the vehicle operator have typically been mounted in the steering column of the vehicle and have utilized cushion constructions directly deployable towards the driver. These driver-side cushions are typically of a relatively simple configuration in that they function over a fairly small well-defined area between the driver and the steering column. One such configuration is disclosed in U.S. Pat. No. 5,533,755 to Nelsen et al., issued Jul. 9, 1996, the teachings of which are incorporated herein by reference.
Inflatable cushions for use in the protection of passengers against frontal or side impacts must generally have a more complex configuration since the position of a vehicle passenger may not be well defined and greater distance may exist between the passenger and the surface of the vehicle against which that passenger might be thrown in the event of a collision. Prior cushions for use in such environments are disclosed in U.S. Pat. No. 5,520,416 to Bishop; U.S. Pat. No. 5,454,594 to Krickl; U.S. Pat. No. 5,423,273 to Hawthorn et al.; U.S. Pat. No. 5,316,337 to Yamaji et al.; U.S. Pat. No. 5,310,216 to Wehner et al.; U.S. Pat. No. 5,090,729 to Watanabe; U.S. Pat. No. 5,087,071 to Wallner et al.; U.S. Pat. No. 4,944,529 to Backhaus; and U.S. Pat. No. 3,792,873 to Buchner et al.
The majority of commercially used restraint cushions are formed of woven fabric materials utilizing multifilament synthetic yams of materials such as polyester, nylon 6 or nylon 6,6 polymers. Representative fabrics for such use are disclosed in U.S. Pat. No. 4,921,735 to Bloch; U.S. Pat. No. 5,093,163 to Krummheuer et al.; U.S. Pat. No. 5,110,666 to Menzel et al.; U.S. Pat. No. 5,236,775 to Swoboda et al.; U.S. Pat. No. 5,277,230 to Sollars, Jr.; U.S. Pat. No. 5,356,680 to Krummheuer et al.; U.S. Pat. No. 5,477,890 to Krummheuer et al.; U.S. Pat. No. 5,508,073 to Krummheuer et al.; U.S. Pat. No. 5,503,197 to Bower et al.; and U.S. Pat. No. 5,704,402 to Bowen et al. A two-weave construction airbag cushion is exemplified in U.S. Pat. No. 5,651,395 to Graham et al. but does not discuss the importance of narrow basket-weave single fabric layers.
As will be appreciated, the permeability of an airbag cushion structure is an important factor in determining the rate of inflation and subsequent rapid deflation following the impact event. Different airbag cushions are utilized for different purposes. For instance, some airbag cushions are installed within inflation modules for driver protection within the steering column of an automobile. Others are utilized as protection for front seat passengers and are installed in and around the glove compartment and/or on the dashboard in front of such a passenger seat. Still others have been developed in an effort to protect all passengers during a long-duration impact event, such as, for example, a rollover collision. In those types of crashes, the target airbag cushion must inflate quickly under high pressure (such as between about 10 and 40 psi) and remain inflated at a relatively high pressures in order to provide the greatest degree of protection to such passengers. Furthermore, such long-duration airbag cushions preferably comprise xe2x80x9cpillowxe2x80x9d formations created through the attachment of at least two different fabrics or fabric ends together and sealed, sewn, or the like, together. Upon inflation the free space between the attachment points inflate as well, thereby producing the desired cushioned xe2x80x9cpillowxe2x80x9d structures. Such long-duration, xe2x80x9cpillowedxe2x80x9d structures have been disclosed in the prior art as airbag cushions within U.S. Pat. No. 5,788,270 to Halano. However, in order to provide a suitable, effective airbag fabric and cushion comprising two or more points of attachment between fabrics or fabric ends, there has been a need to improve upon the structural integrity of the seams at such attachment points to prevent unwanted and potentially harmful leakage of gas or air from within the target airbag cushion. The prior art has discussed the development of coatings to place over the sewn seams at such attachment points in order to seal the potentially loose portions of such seams and/or to keep the individual yams of the airbag fabrics at the attachment points stationary in order to prevent yam shifting and thus possible openings for air or gas leakage. However, such coatings are actually supplemental to the seam structures in providing the necessary barrier to air or gas. A strong, effective, efficient weave construction is the primary method of initially producing an effective airbag fabric for incorporation within an airbag cushion.
These prior xe2x80x9cpillowedxe2x80x9d airbag cushions, however, have been produced solely through specific weaving patterns at the attachment points between the two fabric layers. The possibility of stitch movement during inflation is very high with such airbag cushions. As a result, very thick coatings, as noted above, are required to sustain very low air permeability over the fabric during and after an inflation event. Furthermore, individual sewn seams do not provide consistently low air permeability without utilization of large amounts of relatively expensive coating compositions for the same reasons. The strength and integrity of such seams, particularly present at the surfaces of both fabric layers, are not present without some type of coating to prevent the escape of air during high pressurization of the fabric. Such overall, highly coated, inflatable fabric structures may possess the necessary air permeability characteristics required for proper functioning within a side curtain airbag cushion; however, the costs are extremely high with the amounts of required coatings and the barrier to air leakage provided by such coatings is still suspect (yarn shifting will most likely occur during an inflation event which may produce discontinuities in the integrity of the coating which may in turn compromise the long-term air permeability required for certain airbag applications). Alternatives which permit the utilization of an inflatable two-layer fabric alone (or with substantially reduced amounts of necessary coating materials) that provide very strong seams to form xe2x80x9cpillowedxe2x80x9d structures within such fabrics upon inflation and that do not comprise excessive attachment points between two fabric layers (which would permit dislocation of substantial numbers of stitches that would invariably increase the air permeability rate of the target fabric) would be highly desired in comparison with the costly products now commercially available. To date, the prior art has not accorded the airbag market with such an advancement in this area.
In view of the foregoing, it is a general object of the present invention to provide an inflatable fabric comprising at least one connecting material which forms a peel seam with the individual components of the inflatable which becomes a shear seam upon inflation. It is a more particular object of the present invention to provide an inflatable fabric with at least two layers of fabric which forms pillowed structures upon inflation without the utilization of or need for sewn seams or specific woven structures. Also, an object of this invention is for the utilization of such inflatable fabrics as airbag cushions within a vehicle restraint system. The term xe2x80x9cvehicle restraint systemxe2x80x9d is intended to mean both inflatable occupant restraining cushion and the mechanical and chemical components (such as the inflation means, ignition means, propellant, and the like).
To achieve these and other objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides an inflatable fabric comprising at least two layers of fabric in certain discrete areas of the fabric and at least one connecting material, preferably having a first and second end and a front and back side, interposed between said two layers of fabric and simultaneously attached to said two layers of fabric wherein said first end is attached to one layer and said second end is attached to the other layer. Preferably, such inflatable fabrics and connecting materials are all woven in structure.
The term xe2x80x9cinflatable fabricxe2x80x9d is intended to encompass any fabric that is constructed of at least two layers of fabric which can be sealed to form a bag article. The inventive inflatable fabric thus must include double layers of fabric to permit such inflation, as well as single layers of fabric either to act as a seal at the ends of such fabric panels, or to provide xe2x80x9cpillowedxe2x80x9d chambers within the target fabric upon inflation. The term xe2x80x9call-wovenxe2x80x9d as it pertains to the inventive fabric thus requires that the inflatable fabric having double and single layers of fabric be produced solely upon a loom. Any type of loom may be utilized for this purpose, such as water-jet, air-jet, rapier, dobby, and the like.
The utilization of such peel-seam producing connecting materials which, when simultaneously attached to both fabric components of the inflatable structure form shear seams upon inflation, provides a number of heretofore unexplored benefits within inflatable fabric structures. For example, such a connecting material (which is preferably C-shaped) provides a peel seam with each individual layer of fabric upon contact and attachment. However, upon inflation, the peel seams are actually translated to shear seams. Peel seams are well known in the fabric art as attachments between separate layers or portions of fabrics which are pulled apart through a peeling motion between the two layers (i.e., peeled apart in two opposite directions both perpendicular to the two layers). Shear seams, on the other hand, require shear force to detach one layer from the other (i.e., sheared apart in two opposite directions parallel to the two layers). Shear seams are greater in strength than peel seams since the force required to detach, separate, or otherwise destroy the seam must compensate for the force of the seam 180xc2x0 opposite of the shearing force. Thus, the presence of shear seams provides much greater strength to the two layer article than with merely peel seams. Furthermore, such connecting materials providing shear seams upon inflation permits a simplified manufacturing procedure by placing such materials between two separate fabric layers and attaching each component simultaneously. Such an attachment may be performed through any well known method, such as sewing, gluing, weaving, and the like. However, most preferably, and in order to avoid the potential problems with yarn dislocation associated with stitching and the need then for greater amounts of undesirable expensive coating materials, the seams are formed through RF-welding techniques, such as those disclosed in U.S. patent applications Ser. No. 09/326,368 to Kesh et al. and Ser. No. 09/406,000 to Kesh. Such techniques involve the production of polymeric beads that adhere the fabrics together and also do not permit air to transfer through the weld itself Such an efficient process thus translates into cost savings for the consumer. Additionally, such preferred C-shaped materials, providing such strong seams, permit the omission of large amounts of coatings in order to seal the inflatable fabric for permeability reduction. Further methods of attaching these C-shaped materials include adhesives in film, gel, viscous liquid, or solid form.
Although C-shaped connecting materials are highly preferred (due to their ability to unfold upon inflation and thus permit expansion of the inflatable structure to a certain degree prior to existence of the desired shear seam configuration), other shapes are also possible. Most notably, and without limitation, the connecting materials, may also be X-shaped (thereby providing two locations of attachment on each fabric layer), H-shaped (which also provides two locations of attachment per fabric layer), U-shaped (two locations of attachment, too), Y-shaped (same), Z-shaped (possibly the same), or W-shaped (with either three attachment on one fabric and two on another, or alternating patterns of such attachments). The X-shaped materials provide similar benefits of expansion upon inflation as well as balanced inflation pressure on each portion of the connecting materials during inflation (i.e., each segment of X-shaped materials will be subjected to the same pressures) as do the C-shaped materials. Other shapes may be utilized; the only limitation is that any such materials must create shear seams when attached to the two fabric layers both during and after inflation of the inflatable fabric structure.
The inflatable fabric itself is preferably produced from all-synthetic fibers, such as polyesters and polyamides, although natural fibers may also be utilized in certain circumstances. Preferably, the fabric is constructed of nylon-6,6. The individual yarns utilized within the fabric substrate must generally possess deniers within the range of from about 40 to about 840; preferably from about 100 to about 630. The preferred connecting (again such as, but not limited to, C-shaped materials) are preferably fabric in structure. More preferably they are woven and most preferably they are the same structure as utilized for the two layers of fabric themselves.
Coatings may be applied to the surface as a necessary supplement to the air permeability of the inventive fabric. Since one preferred ultimate use of this inventive fabric is as a side curtain airbag which must maintain a very low degree of air permeability throughout a collision event (such as a rollover where the curtain must protect passengers for an appreciable amount of time), a decrease in permitted air permeability is highly desirable. Any standard coating, such as a silicone, polyurethane, polyamide, polyester, rubber (such as neoprene, for example), and the like, may be utilized for this purpose and may be applied in any standard method and in any standard amount on the fabric surface.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice for the invention. It is to be understood that both the foregoing general description and the following detailed description of preferred embodiments are exemplary and explanatory only, and are not to be viewed as in any way restricting the scope of the invention as set forth in the claims.